This article seeks to cast light on the role of think-tanks in policy making during the New Labour era. It assesses the extent to which the Labour government under Tony Blair, in its first term in office, made use of policy expertise from think-tanks to shape its social policy agenda. This policy field is appropriate for scrutiny because of its centrality in relation to New Labour's core values and policy agenda. Moreover, Blair's term in office during this period has been referred to as `government by think-tanks', leading a number of political scientists to ask whether think-tanks as private, government-external institutions actually `make a difference'. The article is based on interviews with analysts from think-tanks, civil servants and politicians, as well as analysis of key documents. The article concludes that Labour, once in government, made little use of those think-tanks, which had supported the party modernisers in opposition. With the party in government, the civil service emerged as the most important actor in the design of social policy. A further important finding is that think-tank involvement -- or the lack of it -- in the policy process offers insights into broader changes in the British state.